Mounjaro®
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Start journey Learn moreMounjaro vs Ozempic: what the evidence, the licences, and your situation actually tell you
The licence question that decides everything
Start here, because getting this wrong is expensive. Ozempic is semaglutide (the same active molecule as Wegovy) but the MHRA has authorised it specifically for type 2 diabetes management, not weight loss. Prescribing it for weight loss in the UK is an off-label use, and the NHS does not support that route. Mounjaro (tirzepatide), by contrast, holds a full UK licence for weight management in adults with a BMI of 30 or above, or a BMI of 27 or above alongside a weight-related condition such as high blood pressure or sleep apnoea.
The NHS medicines page for tirzepatide sets this out plainly. If someone is offering you Ozempic as a weight-loss treatment, that is worth a conversation with a prescriber before you proceed. The medicine licensed for weight loss in its own right is either Mounjaro or Wegovy, which contains semaglutide at the weight-loss dose and under the weight-loss licence.
This distinction is not a technicality. It affects what clinical oversight you should expect, what evidence underpins the dosing, and (critically) what is and is not legal to advertise or prescribe for this purpose.
Different molecules, different mechanisms
Ozempic works on a single pathway: it activates GLP-1 receptors, which slow digestion, blunt appetite signals and help regulate blood sugar. Mounjaro does that too, but it also activates GIP receptors, making it the only dual-agonist weight-loss medicine licensed in the UK. The practical consequence of that second pathway is visible in the trial data.
In SURMOUNT-1, which randomised around 2,500 adults with obesity, participants on the highest tirzepatide dose lost an average of roughly 20–21% of body weight over 72 weeks, as published in the New England Journal of Medicine. In the STEP 1 trial, semaglutide 2.4mg (Wegovy's dose, not Ozempic's) produced an average loss of around 15% over 68 weeks. Ozempic's diabetes dosing is different again, and no head-to-head weight-loss trial compares it directly to Mounjaro, that comparison would be Mounjaro versus Wegovy, which is a separate question explored in detail on this page.
The mechanism difference matters for side effects too. Both carry a GI-led profile: nausea, loose stools, constipation, reflux. The pattern is similar because the GLP-1 pathway is shared. The MHRA monitors both under its Black Triangle (▼) scheme, meaning unusual side effects should be reported via the Yellow Card scheme.
A comparison at a glance
| Feature | Mounjaro (tirzepatide) | Ozempic (semaglutide) |
|---|---|---|
| UK weight-loss licence | Yes) BMI ≥30, or ≥27 with a weight-related condition | No (licensed for type 2 diabetes only |
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist only |
| Dosing schedule | Starts 2.5mg; titrated up to 15mg (prescriber-directed) | Starts 0.25mg; titrated up to 1mg for diabetes use |
| Average weight loss (trial evidence) | ~20–21% at 15mg (SURMOUNT-1, NEJM) | Not studied at these doses for weight loss; Wegovy 2.4mg ~15% (STEP 1) |
| NICE recommendation for weight management | Yes) TA1026 (published December 2024) | No, TA875 covers Wegovy, not Ozempic |
| Dispensed by nume for weight loss | Yes | No |
NICE's appraisal of tirzepatide (TA1026) recommended Mounjaro for NHS use in adults with a BMI of 35 or above and at least one weight-related comorbidity, with lower thresholds for some ethnic backgrounds. Ozempic does not appear in that recommendation, Wegovy does, under a separate appraisal.
So which should you actually be thinking about?
If you are researching weight loss, the relevant decision is almost certainly between Mounjaro and Wegovy, two separately licensed medicines with overlapping eligibility but different mechanisms and different evidence profiles, and if you want to understand the key differences between Wegovy and Mounjaro before your consultation, that comparison is worth reading carefully. That comparison is worth reading carefully before your consultation.
Ozempic is not part of that decision for most people. It is a diabetes medicine, and its supply has been under ongoing strain precisely because demand for it as an off-label weight-loss treatment has disrupted access for people who need it for blood-sugar control. The MHRA and NHS have been clear on this point, and it is equally important to understand that combining semaglutide and tirzepatide is not a safe or recommended approach.
At nume, our prescribers hold a GPhC-registered Independent Prescribing qualification and review every application personally. If Mounjaro is clinically suitable, your prescription is issued the same day and dispatched to arrive the next working day. Which medicine suits your situation is a clinical decision our prescribers make with you, not something any comparison page can settle. The right place to start is your free consultation.
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